Field
Exemplary embodiments of the present disclosure relate to a light emitting diode and a method of manufacturing the same, and more particularly, to a light emitting diode that has low contact resistance between a semiconductor layer having a non-polar or semi-polar growth plane and an electrode, and a method of manufacturing the same.
Discussion of the Background
Recently, with increasing demand for high output light emitting diodes, there is increasing demand for vertical light emitting diodes having good heat dissipation efficiency and luminous efficacy. For a vertical light emitting diode, a growth substrate is separated from semiconductor layers to improve light extraction efficiency by increasing roughness of a separated surface and a metal substrate is attached to an overall upper surface of a P-type semiconductor layer in order to improve heat dissipation efficiency. With this structure, the vertical type light emitting diode can be applied to high output light emitting diodes driven at high current density.
Generally, a light exit surface of the vertical type light emitting diode is present on one surface of an n-type semiconductor layer exposed due to separation of the growth substrate. A surface of the p-type semiconductor layer opposite the light exit surface is formed with components for reflecting light, for example, a reflective electrode layer such as an Ag layer. Japanese Unexamined Patent Publication No. 2010-56423 discloses a technology in which heat treatment is performed in order to reduce contact resistance of the Ag layer while maintaining reflection characteristics thereof.
Recently, output and reliability requirements of light emitting diodes used in various applications are much higher than those of typical light emitting diodes. Accordingly, research and development of techniques for manufacturing a vertical light emitting diode by growing nitride semiconductor layers on a growth substrate having a non-polar or semi-polar growth plane are actively conducted. Such vertical light emitting diodes having nonpolar or semi-polar growth planes exhibit low efficiency drooping compared with light emitting diodes having polar growth planes and thus are suitable for high power light emitting diodes.
However, in a nitride semiconductor layer grown on such a nonpolar or semi-polar growth plane, contact resistance of a reflective electrode including a P-type semiconductor layer and Ag is much higher than that of a nitride semiconductor layer grown on the C-plane. Moreover, when heat treatment disclosed in Japanese Unexamined Patent Publication No 2010-56423 and the like is performed on the reflective electrode in order to lower contact resistance, reflection characteristics are deteriorated, thereby causing significant deterioration in luminous efficacy of the light emitting diode.